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Change how mirror writes are handled, according to the discussion on the

Browse Source 
mailing list.

When initiating a write, ccdbuffer() returns two "struct ccdbuf *"s
linked together by the cb_mirror field.  "cb_pflags &
CCDPF_MIRROR_DONE" is set to 0 on both of them.

When a component returns to ccdiodone(), it checks if "cb_pflags &
CCDPF_MIRROR_DONE" is set or not.  If not, it sets the partner's
flag and returns.  If it is, it means its partner has already
returned, so it will go to the regular cleanup (which is in the
fallthrough code).

There should be no performance or functionality changes unless the
higher-level scsi driver does something with the resid value.  The change
is purely aesthetical and prepares us for the parity implementation.
This commit is contained in:
asami 1996-03-26 02:29:11 +00:00
parent eae3c9253f
commit b50b9c7209
2 changed files with 78 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
sys/dev/ccd/ccd.c
View File

@ -1,4 +1,4 @@
/* $Id: ccd.c,v 1.7 1996/01/31 11:25:46 asami Exp $ */
/* $Id: ccd.c,v 1.8 1996/03/21 04:13:25 asami Exp $ */
/* $NetBSD: ccd.c,v 1.22 1995/12/08 19:13:26 thorpej Exp $ */
@ -136,13 +136,32 @@ int ccddebug = CCDB_FOLLOW | CCDB_INIT | CCDB_IO | CCDB_LABEL | CCDB_VNODE;
#define ccdunit(x) dkunit(x)
#define ccdpart(x) dkpart(x)
/*
This is how mirroring works (only writes are special):
When initiating a write, ccdbuffer() returns two "struct ccdbuf *"s
linked together by the cb_mirror field. "cb_pflags &
CCDPF_MIRROR_DONE" is set to 0 on both of them.
When a component returns to ccdiodone(), it checks if "cb_pflags &
CCDPF_MIRROR_DONE" is set or not. If not, it sets the partner's
flag and returns. If it is, it means its partner has already
returned, so it will go to the regular cleanup.
*/
struct ccdbuf {
struct buf cb_buf; /* new I/O buf */
struct buf *cb_obp; /* ptr. to original I/O buf */
int cb_unit; /* target unit */
int cb_comp; /* target component */
int cb_pflags; /* mirror/parity status flag */
struct ccdbuf *cb_mirror; /* mirror counterpart */
};
/* bits in cb_pflags */
#define CCDPF_MIRROR_DONE 1 /* if set, mirror counterpart is done */
#define getccdbuf() \
((struct ccdbuf *)malloc(sizeof(struct ccdbuf), M_DEVBUF, M_WAITOK))
#define putccdbuf(cbp) \
@ -703,10 +722,7 @@ ccdstrategy(bp)
if (bounds_check_with_label(bp, lp, wlabel) <= 0)
goto done;
if (cs->sc_cflags & CCDF_MIRROR && (bp->b_flags & B_READ) == 0)
bp->b_resid = bp->b_bcount*2;
else
bp->b_resid = bp->b_bcount;
bp->b_resid = bp->b_bcount;
/*
* "Start" the unit.
@ -896,6 +912,11 @@ ccdbuffer(cb, cs, bp, bn, addr, bcount)
cbp->cb_buf.b_vp = ci2->ci_vp;
cbp->cb_comp = ci2 - cs->sc_cinfo;
cb[1] = cbp;
/* link together the ccdbuf's and clear "mirror done" flag */
cb[0]->cb_mirror = cb[1];
cb[1]->cb_mirror = cb[0];
cb[0]->cb_pflags &= ~CCDPF_MIRROR_DONE;
cb[1]->cb_pflags &= ~CCDPF_MIRROR_DONE;
}
}
@ -923,10 +944,7 @@ ccdintr(cs, bp)
dk_busy &= ~(1 << cs->sc_dk);
#endif
if (bp->b_flags & B_ERROR)
if (cs->sc_cflags & CCDF_MIRROR && (bp->b_flags & B_READ) == 0)
bp->b_resid = bp->b_bcount*2;
else
bp->b_resid = bp->b_bcount;
bp->b_resid = bp->b_bcount;
biodone(bp);
}
@ -965,6 +983,18 @@ ccdiodone(cbp)
unit, bp->b_error, cbp->cb_comp);
#endif
}
if (ccd_softc[unit].sc_cflags & CCDF_MIRROR &&
(cbp->cb_buf.b_flags & B_READ) == 0)
if ((cbp->cb_pflags & CCDPF_MIRROR_DONE) == 0) {
/* I'm done before my counterpart, so just set
partner's flag and return */
cbp->cb_mirror->cb_pflags |= CCDPF_MIRROR_DONE;
putccdbuf(cbp);
splx(s);
return;
}
count = cbp->cb_buf.b_bcount;
putccdbuf(cbp);

48
sys/geom/geom_ccd.c
View File

@ -1,4 +1,4 @@
/* $Id: ccd.c,v 1.7 1996/01/31 11:25:46 asami Exp $ */
/* $Id: ccd.c,v 1.8 1996/03/21 04:13:25 asami Exp $ */
/* $NetBSD: ccd.c,v 1.22 1995/12/08 19:13:26 thorpej Exp $ */
@ -136,13 +136,32 @@ int ccddebug = CCDB_FOLLOW | CCDB_INIT | CCDB_IO | CCDB_LABEL | CCDB_VNODE;
#define ccdunit(x) dkunit(x)
#define ccdpart(x) dkpart(x)
/*
This is how mirroring works (only writes are special):
When initiating a write, ccdbuffer() returns two "struct ccdbuf *"s
linked together by the cb_mirror field. "cb_pflags &
CCDPF_MIRROR_DONE" is set to 0 on both of them.
When a component returns to ccdiodone(), it checks if "cb_pflags &
CCDPF_MIRROR_DONE" is set or not. If not, it sets the partner's
flag and returns. If it is, it means its partner has already
returned, so it will go to the regular cleanup.
*/
struct ccdbuf {
struct buf cb_buf; /* new I/O buf */
struct buf *cb_obp; /* ptr. to original I/O buf */
int cb_unit; /* target unit */
int cb_comp; /* target component */
int cb_pflags; /* mirror/parity status flag */
struct ccdbuf *cb_mirror; /* mirror counterpart */
};
/* bits in cb_pflags */
#define CCDPF_MIRROR_DONE 1 /* if set, mirror counterpart is done */
#define getccdbuf() \
((struct ccdbuf *)malloc(sizeof(struct ccdbuf), M_DEVBUF, M_WAITOK))
#define putccdbuf(cbp) \
@ -703,10 +722,7 @@ ccdstrategy(bp)
if (bounds_check_with_label(bp, lp, wlabel) <= 0)
goto done;
if (cs->sc_cflags & CCDF_MIRROR && (bp->b_flags & B_READ) == 0)
bp->b_resid = bp->b_bcount*2;
else
bp->b_resid = bp->b_bcount;
bp->b_resid = bp->b_bcount;
/*
* "Start" the unit.
@ -896,6 +912,11 @@ ccdbuffer(cb, cs, bp, bn, addr, bcount)
cbp->cb_buf.b_vp = ci2->ci_vp;
cbp->cb_comp = ci2 - cs->sc_cinfo;
cb[1] = cbp;
/* link together the ccdbuf's and clear "mirror done" flag */
cb[0]->cb_mirror = cb[1];
cb[1]->cb_mirror = cb[0];
cb[0]->cb_pflags &= ~CCDPF_MIRROR_DONE;
cb[1]->cb_pflags &= ~CCDPF_MIRROR_DONE;
}
}
@ -923,10 +944,7 @@ ccdintr(cs, bp)
dk_busy &= ~(1 << cs->sc_dk);
#endif
if (bp->b_flags & B_ERROR)
if (cs->sc_cflags & CCDF_MIRROR && (bp->b_flags & B_READ) == 0)
bp->b_resid = bp->b_bcount*2;
else
bp->b_resid = bp->b_bcount;
bp->b_resid = bp->b_bcount;
biodone(bp);
}
@ -965,6 +983,18 @@ ccdiodone(cbp)
unit, bp->b_error, cbp->cb_comp);
#endif
}
if (ccd_softc[unit].sc_cflags & CCDF_MIRROR &&
(cbp->cb_buf.b_flags & B_READ) == 0)
if ((cbp->cb_pflags & CCDPF_MIRROR_DONE) == 0) {
/* I'm done before my counterpart, so just set
partner's flag and return */
cbp->cb_mirror->cb_pflags |= CCDPF_MIRROR_DONE;
putccdbuf(cbp);
splx(s);
return;
}
count = cbp->cb_buf.b_bcount;
putccdbuf(cbp);